Moisture regime of historical sandstone masonry — A numerical study

Abstract

Abstract Rising damp causes deterioration of masonry walls in many historical buildings. Although the phenomenon of capillary rise in porous structures is relatively well understood, reliable numerical modeling of the moisture regime, applicable to the assessment of current state as well as to the predictions of changes induced by various corrective moisture-reduction measures, remains a challenge. This paper presents the results of a numerical modeling study dealing with the moisture regime of a masonry wall of the baroque Church of All Saints in Heřmankovice. The numerical approach used is based on general concepts of mass conservation and Darcian flow of capillary water in porous media. The model was parameterized and validated using experimental data obtained by on-site survey, laboratory analysis and monitoring. The modeling results confirmed our hypothesis that, in a long-term perspective, the second-stage evaporation—controlled by the hydraulic properties of the masonry—prevails over the first-stage evaporation—controlled by the atmospheric conditions—for most simulation scenarios conducted. Of the two corrective moisture-reduction measures considered, i.e. a closed drain versus open drain installation, the latter was found to be significantly more effective, leading to a greater reduction of moisture in the masonry.